Four soybean (Glycine max (L.) Merrill) cultivars from China were studied to determine the inheritance of their resistant reactions to soybean mosaic virus (SMV) strain G1. Each of the cultivars was crossed with a susceptible cultivar Williams to determine the number of genes for resistance. The four cultivars were also crossed with lines with known genes for resistance to SMV to test for allelism. The crosses were evaluated in the F$\sb2$ and with F$\sb{2:3}$ families in the field and in the greenhouse for reaction to inoculation with SMV-G1. Results show that each of the Chinese cultivars has a single dominant gene for resistance to SMV-G1. The resistance gene carried by Feng Shou Huang is at the Rsv1 locus. The resistance gene carried by Ke Feng No.1 is at the non-Rsv1 locus in PI 486.355. The resistance genes carried by Da Bai Ma and Xu Dou No.1 are at neither the Rsv1 locus nor the non-Rsv1 locus in PI 486.355.Seventy-three SMV isolates obtained from 500 new accessions from nine provinces in central China were classified based on reactions on seven soybean differentials. G1 was the predominant SMV strain among the nine provinces. G2 was the predominant SMV strain in the accessions from Hebei province. G3 had the second widest distribution. Very few isolates of G4, G5 and G6 were found and no G7 was found. No clear pattern of relationships exist between the geographical origin and diversity of SMV strains, possibly due to the small sample size.A study identifying SMV resistant U.S. soybean ancestors showed that eight ancestors, CNS, Ogden, Haberlandt, FC 31.745, Peking, PI 71.506, PI 88.788 and Tokyo were resistant. It is the first time that six of the eight ancestors have been reported as resistant to SMV. CNS is the most common SMV-resistance donor in U.S. public soybean cultivars. Ogden and Haberlandt are often found in U.S. resistant cultivars' pedigrees. FC 31.745, PI 71.506, PI 88.788 and Tokyo are potential donors to at least one reported SMV-resistant cultivar.